This invention relates generally to refrigeration defrost systems and more particularly to a defrost water drain system for use in a refrigerator.
As is known, refrigerator and freezer systems, especially of the home appliance type, provide cooled air to an enclosure in which food and the like can be stored, thereby to prolong the edible life of the food. The enclosures, namely fresh food compartments and freezer compartments, are cooled by air blown over a heat exchanger or evaporator. The heat exchanger, typically located in an evaporator enclosure in the freezer compartment, extracts heat from the air thereby producing cooled air. The heat exchanger generally operates on the known cooling effect provided by gas that is expanded in a closed circuit, i.e., the refrigeration cycle. However, to be expanded, the gas must also be compressed and this is accomplished by the use of a compressor. During operation of the compressor, an evaporator fan moves air across the evaporator for assisting in heat transfer.
The efficiency of such systems can be enhanced by reducing the amount of frost that builds up on the heat exchanger, as is known. Modern systems are generally of the self-defrosting type. To this end, they employ a heater specially positioned and controlled to slightly heat the heat exchanger to cause melting of frost build-up on the heat exchanger. These defrost heaters are controlled pursuant to defrost cycle algorithms and configurations.
As the defrost heater warms the evaporator, defrost water resultant from the melting of frost build-up, drips from the evaporator and is typically collected into a drip tray disposed below the evaporator. Drain tubing is connected to the drip tray and directly drains the defrost water to an evaporator pan which is generally located below the freezer compartment in a compressor compartment adjacent a condenser and condenser fan for promoting evaporation of the defrost water delivered to the evaporator pan.
Such a system, however, has disadvantages. Specifically, the conventional defrost water drain tubing has a detrimental effect on the efficiency of the refrigerator. During compressor operation, the evaporator fan draws air across the evaporator and creates a lower partial pressure in the evaporator enclosure wherein hot, moist air from the compressor compartment is drawn into the evaporator compartment through the drain tubing. Additionally, when the compressor and evaporator fan are not operating, the cold air within the food compartment, being relatively more dense than the external ambient air, flows through the drain tubing out of the evaporator enclosure and into the ambient environment during normal compressor operation. This flowing of cold air out of the evaporator compartment results in warm air migrating into the food storage compartments. Therefore, both when the compressor and evaporator fan are operating and when they are not operating, undesirable transfer of air may occur through the defrost water drain tubing resulting in a thermal leak. It can be understood by one skilled in the art, that these types of thermal leaks are detrimental to the overall efficiency of a refrigerator.